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Citation and License

Nanoscale Res Lett 2011, 6:24
doi:10.1007/s11671-010-9768-x

Published: 2 September 2010

Abstract

Here, we report a straightforward synthesis process to produce colloidal Eu3+-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene
glycol) serves as a high-boiling point solvent allowing for nanoscale particle formation
as well as a convenient medium for solvent exchange and subsequent surface modification.
The La(OH)3:Eu3+ NPs produced by this process were ~3.5 nm in diameter as determined by transmission
electron microscopy. The NP surface was coated with aminopropyltriethoxysilane to
provide chemical functionality for attachment of biological ligands, improve chemical
stability and prevent surface quenching of luminescent centers. Photoluminescence
spectroscopy of the NPs displayed emission peaks at 597 and 615 nm (λex = 280 nm). The red emission, due to 5D0 → 7F1 and 5D0 → 7F2 transitions, was linear with concentration as observed by imaging with a conventional
bioimaging system. To demonstrate the feasibility of these NPs to serve as optical
probes in biological applications, an in vitro experiment was performed with HeLa
cells. NP emission was observed in the cells by fluorescence microscopy. In addition,
the NPs displayed no cytotoxicity over the course of a 48-h MTT cell viability assay.
These results suggest that La(OH)3:Eu3+ NPs possess the potential to serve as a luminescent bioimaging probe.